template<classK>boolcontains(constK&x)const; (2)(C++20 起) 1)检查容器中是否有关键等价于key的元素。 2)检查是否有键比较等价于值x的元素。此重载仅若有限定标识Hash::is_transparent与KeyEqual::is_transparent均合法并指代类型才参与重载决议。这假设能用K和Key类型一起调用这种Hash,还有KeyEqual是通透的...
boolcontains(constKey&key)const; (1)(C++20 起) template<classK>boolcontains(constK&x)const; (2)(C++20 起) 1)检查容器中是否有元素的键等价于key。 2)检查是否有元素的键比较等价于值x。此重载只有在Hash::is_transparent与KeyEqual::is_transparent均合法并指代类型时才会参与重载决议。这假设使得Has...
unordered_map 是关联容器,含有带唯一键的键-值 pair 。搜索、插入和元素移除拥有平均常数时间复杂度。 元素在内部不以任何特定顺序排序,而是组织进桶中。元素放进哪个桶完全依赖于其键的哈希。这允许对单独元素的快速访问,因为一旦计算哈希,则它准确指代元素所放进的桶。
#include <unordered_map>#include <iostream>intmain(){std::unordered_map<int,char>nums{{1,'a'},{3,'b'},{5,'c'},{7,'d'}};std::cout<<"nums contains "<<nums.size()<<" elements.\n";} 输出: nums contains 4 elements.
std::unordered_map template<classKey,// unordered_map::key_typeclassT,// unordered_map::mapped_typeclassHash= hash<Key>,// unordered_map::hasherclassPred = equal_to<Key>,// unordered_map::key_equalclassAlloc = allocator< pair<constKey,T> >// unordered_map::allocator_type>classunordered...
如C++的名著《The C++ Standard Library》中所述: “A map is a sorted associative container that contains key-value pairs with unique keys. Keys are sorted by using the comparison function Compare…The complexity for searching operations is logarithmic in the size of the containers.”(map是一个排...
下列代码用 size 显示std::unordered_map 中的元素数: 运行此代码 #include <unordered_map> #include <iostream> int main() { std::unordered_map<int,char> nums {{1, 'a'}, {3, 'b'}, {5, 'c'}, {7, 'd'}}; std::cout << "nums contains " << nums.size() << " elements.\n...
unordered_map::contains (C++20) unordered_map::equal_range Bucket interface unordered_map::begin(size_type)unordered_map::cbegin(size_type) unordered_map::end(size_type)unordered_map::cend(size_type) unordered_map::bucket_count unordered_map::max_bucket_count unordered_map::bucket_size unordere...
Number of buckets: 1109 Bucket 0 contains 1000 elements. All the elements ended up in one bucket. This is because I intentionally made the keys a multiple of 1109 which happens to be the same as the number of buckets. It's easy to see why if you remember the formula for finding the ...
contains (C++20) 检查容器是否含有带特定键的元素 (公开成员函数) equal_range 返回匹配特定键的元素范围 (公开成员函数) 桶接口 begin(size_type)cbegin(size_type) 返回一个迭代器,指向指定的桶的开始 (公开成员函数) end(size_type)cend(size_type) ...